HU216987B - Parts for printed circuit boards - Google Patents

Abstract

A component for use in manufacturing articles such as printed circuit boards comprising a laminate of a sheet of copper foil and a sheet of metal or the like. A band of flexible adhesive joins the sheets around their borders and creates a protected central zone at the interface of the sheets. Islands of adhesive are located inwardly of the edges of the sheets through which tooling pin holes may be formed to facilitate handling of the foil.

Description

FIELD OF THE INVENTION The present invention relates to a component for a printed circuit board in particular.

In its simplest design, a printed circuit board contains a dielectric layer made of epoxy-resin impregnated glass fiber, commonly known as "prepreg". Copper foil layers are bonded to both sides of the dielectric layer. During the use of this printed circuit board, copper is etched in several process steps to form guides on the surface of the dielectric layer. This assembly is often referred to as a printed circuit board or sandwich core.

In manufacturing processes, it is not unusual for several or such basic components of the type described above or components with additional layers to be stacked vertically. This assembled stack is called a "book." The book is heated and then pressed. After cooling and drying, the individual sheets thus combined are separated and processed in the usual manner. This general technique, which is followed in many places, is described in detail in U.S. Patent No. 4,875,283. One of the most important points in the manufacturing process is to keep the copper foil layers clean or to avoid contamination. This is important in any case, even if the printed circuit board is a simple sandwich structure consisting of an insulating dielectric layer between two outer copper foil layers, but also in the case of multiple printed circuit boards assembled from such sandwich cores.

One of the main causes of contamination of copper foil layers is the presence of various foreign materials that are generated or deposited during the pre-production, cutting, transport and storage operations of resin powder, glass fibers, hairs, dust particles and the dielectric layer. When placing printed circuit boards in a book, great care is taken to remove the resin powder using various wiping techniques. However, it is undeniable that, despite the best efforts, a certain amount of resin powder and other contaminants remain on the surface of the copper foil layers. During the laminating process, under the influence of heat and pressure, this resin powder melts, which appears as spots or deposits on the copper surfaces.

Another problem is the appearance of various cavities and recesses in the surface of the copper foil layers. On the one hand, these may be derived from resin imprints on the copper foil during the heating and laminating process, which may be imprinted on the copper, but may also occur during the treatment of the very thin foil, since there is no known method to completely eliminate the presence of resin powder. , although there are many efforts to resolve the issue in many directions.

The presence of traces, depressions, or undesirable deposition of the molten resin on the copper surface, which is then reconstituted, usually results in failure, such as short circuiting or rupture of the finished product. There are many conductors on such a finished printed circuit board. If a recess is formed in the foil in the area where two conductors are to be formed in subsequent operations, that recess will be filled and in many cases will cause an electrical short circuit. Conversely, the same recess may cause a rupture if it occurs exactly in the position of one of the conductors to be formed, thereby interrupting the conductor continuity.

In today's technology, printed circuit board conductors are typically formed with a width of 10 µm and the same distance between two adjacent conductors. However, industrial demands and current trends in the direction of the industry are moving towards making managers and spaces between managers even smaller, for example around 5 pm. If the copper surface used for the printed circuit board is imperfect, either short circuits or openings can occur, rendering most of these printed circuit boards unusable. Although printed circuit boards can in principle be repaired, in more modern and high-performance technology systems, repair is not economical and such faulty printed circuit boards are useless waste.

A common cause of blemishes is the treatment of the film. As each film layer and dielectric layer are superimposed, their position is secured by pins that extend upward from a tool plate. The tool plate is usually a thick steel plate that forms the bottom of the pile. Each layer, whether copper foil or dielectric, or semi-finished laminated sandwich core, has pre-drilled or pre-pressed pre-punched holes, the size and location of which are determined by various industry standards. Each of these layers must be placed by hand on the pins of the tool blade which hold the individual layers in place through these pre-drilled holes or holes.

One of the sides of the finished film is the distinguished guiding surface. The other side is usually treated with an oxidation process to obtain a sufficiently rough surface, usually gray, which provides better bonding with the molten resin during the bonding process. One of the copper foil families in use today is the "half-ounce copper foil," which means that half an ounce, or 14.175 grams of copper, is spread over a surface of 0.093 m ² (1 square foot). This results in a film thickness of about 17.8 µm for a uniform film thickness. In addition, they are used in quarter-octane and octagonal copper foils. It is obvious to everyone that the processing and handling of such thin films poses many problems. Layers of foil of this thickness must be placed over the locating pins by hand, which may cause wrinkles, and wrinkles may also cause defective guiding sections in the finished product.

It is an object of the present invention to provide suitable means for better handling of films, not only to avoid folds or creases, but also to maintain the original purity of the copper foil. Whenever a worker needs a printed circuit board

You must assemble the layers, place a separator sheet on top of the sandwich core, and then continue to stack the layers on the separator board for the next printed circuit board. Thus, during the process, not only the surfaces of the separator board, but also those of each conductive copper foil layer, must be wiped off.

Another reason for the failure of the printed circuit boards is the artificial resin layer that wraps around the pins and solidifies there.

As mentioned above, each layer is placed in the stack by means of locating pins which are necessarily slightly smaller in diameter or size than the pre-formed holes or holes in the copper foil layers and the dielectric layers. As the book is heated and pressed, the molten resin creeps around the positioning pins and generally fills the space between the positioning pins and the pins in the dielectric and copper foil layers. The resin can penetrate not only vertically but also horizontally between the individual layers, especially between the copper foil layers and the separating sheets. After drying, this resin must be removed or subsequently act as an anti-etching agent during etching. In addition, it may also stick to the surface of the copper foil. Not only does the resin spill in the wrong place on the surface of the copper, it also makes it difficult to disassemble the book as the hardened resin hardens on the pins. Each printed circuit board is thus very difficult to remove from the locating pins.

In view of the foregoing, the present invention seeks to achieve three main objectives. One of our main goals is to facilitate the handling of extremely thin copper foil layers. Our second main goal is to ensure that the copper foil remains as free as possible from contamination both before and during the manufacturing process. Our third main objective is to prevent the resin from solidifying around the locating pins and from interfering with each component of the printed circuit board.

SUMMARY OF THE INVENTION This object is primarily solved by a component for use in the manufacture of printed circuit boards and the like, which according to the invention is a laminate comprising at least one layer of copper foil and an aluminum backing layer. The copper foil layer is incorporated into the printed circuit board to form its functional element, such as its guideways, while the aluminum carrier layer forms the removable element of the finished printed circuit board. Each surface of the copper foil layer and the aluminum support layer is substantially free of dirt and is connected to one another in a joint region.

The contaminant-free surfaces are bounded around their circumference by an elastic adhesive strip that defines a substantially zone-free central zone inwardly of the edges of the layers. The aluminum backing layer serves as a reinforcement for the copper foil layer and significantly facilitates its handling.

In addition, the laminated component may be comprised of two layers of copper foil which form the functional elements of a ready-made printed circuit board and the removable element is an aluminum substrate. One inner surface of the copper foil layers on both sides of the aluminum substrate and the two substrates of the aluminum substrate are substantially free of dirt.

Similarly, the resilient adhesive strip connects the non-contaminated surface of the copper foil layers to the opposite non-contaminated surface of the aluminum substrate along the periphery of the aluminum substrate, thereby defining two substantially non-contaminated central zones on and around the periphery of the substrate.

At least a flexible, water-soluble adhesive island can be formed at a predetermined location from the periphery of the bonded layers in a predetermined location that joins the non-contaminating surface of the layers. In the adhesive island, as well as in the layers above and below, a hole or bore is provided to allow the locating pins to enter the laminate. A plurality of such adhesive islands may be disposed inward from the extreme adhesive strip, defining the areas in which the mounting holes are formed during assembly. During manufacture, the adhesive islands prevent the molten resin from penetrating between two superimposed layers.

The above and other features of the invention, including many new details and combinations of components, will be described in more detail with reference to the following drawing. It is to be emphasized that the component according to the invention, which is particularly useful in the manufacture of printed circuit boards, is provided by way of example only, and is not intended to limit the scope of the invention. The essence and features of the present invention may be practiced in many different embodiments without departing from the scope of the present invention. In the drawing it is

Figure 1 is an exploded, exploded view of a pre-laminate schematic cross-section of a conventional multilayer sandwich structure constructed of two printed circuit boards,

Figure 2 is a schematic cross-sectional view of a multilayer sandwich structure of two printed circuit boards similar to that shown in Figure 1, which clearly recognizes details of the construction of the present invention;

Figure 3 is an enlarged, schematic cross-sectional view of an embodiment of a component used in the manufacture of printed circuit boards according to the present invention;

Fig. 4 is a detail similar to Fig. 3 but of a different design

Fig. 5 is a schematic top view of a component of the invention;

Figure 6 is an enlarged view of an adhesive island with a locating pin bore therein.

HU 216 987 Β

Figure 1 is a schematic diagram of a conventional multi-layer sandwich structure of six printed circuit boards comprising six layers. The sandwich structure comprises, from below, a first separating layer 2, which may be made of a conventional polished steel sheet covered with a release paper not shown in the drawing, as described in U.S. Patent No. 4,875,283, or may be a dual-purpose separating and separating layer. and coated on both sides with a siloxazine polymer in a manner known from the foregoing patent document. On the separating layer 2 is placed a first or "outer" layer of copper foil 4 having a "clean", in other words, working surface 6 facing downwards. The upper bonding surface 8 of the copper foil layer 4 is oxidized, which facilitates better bonding of the copper foil layer 4 to the surface above which is a dielectric layer according to the embodiment shown. Above the copper foil layer 4 is a laminated multilayer sandwich core 10 consisting of three dielectric layers 12 and two double-sided foil sheets 14, each of which has guides 15 on each side. To this inner laminated multilayer sandwich core 10 is deposited an additional layer of copper foil 4 having an oxidized bonding surface 16 on the sandwich core 10 and an upper working surface 18 in contact with a subsequent separating layer 2.

The upper working surface 18 of the copper foil layer 4 and the downwardly facing working surface 6 of the lower copper foil layer form the outer working surfaces of the first printed circuit board of the stacked printed circuit boards. After the printed circuit board has been completed, these are etched in a known manner to form a suitable guideway thereon.

Connected to the upper surface 24 of the second separating layer 2 is a book having the same structure as the first, which also has a lower copper foil layer 4, a laminate sandwich core 10 on top thereof, and an upper copper foil layer 2 superimposed thereon. The presented books are typically multilayer, more precisely six-layer units, since the laminated multilayer sandwich core 10 has two foil sheets 14 which add two layers twice, and the sandwich core 10 has two layers of copper foil 4 on both sides with an outer surface of 6.18. means an additional layer. Therefore, the presented book can be considered as a six-layer multi-layer printed circuit board.

Referring now to Figure 2, it is necessary to go slightly beyond the figure and refer to Figure 3, which illustrates the construction of one of the laminate components 30 of the present invention. In addition to the reference numeral, this component 30 is also designated as CAC, which refers to the copper-aluminum structure (initials of its English name). This component 30 comprises a commercial grade aluminum substrate A having a thickness ranging from 25 pm to 3.2 mm, preferably 255 pm to 370 pm, depending on the end use. On the upper surface of the substrate A is a layer of copper foil C, which is made of semi-percussion copper foil for the indicated aluminum thickness. This means that half an ounce, or 14.175 g of copper, is spread over an area of 0.093 m ² . For uniform spreading, the copper foil layer C has a thickness of about 180 µm. Generally speaking, the sizes described are industry standard values for printed circuit boards today.

While substrate A is preferably made of aluminum, other metals, such as stainless steel or nickel alloys, can be used effectively. In some cases, for example when laminating plastic credit cards, polypropylene may be used.

_O outer copper surface shown as the upper surface in Figure 3 C preoxidized and often depending on the gray oxidation doing employed, although as a result of other colors may. The oxidizing effect is intended that this C _o external copper surface is easier hozzáköthessük the dielectric layer that is to be connected to a printed circuit board during manufacturing operations. The inner copper surface of Cj is clean, dirt-free, and is often referred to as "virgin." This surface serves as a functional element in the finished PCB and is etched to produce the desired circuit path configuration. The surface A of the aluminum substrate A, which is in contact with the inner copper surface Cj, is also substantially free of dirt.

The aluminum layer of the second copper foils on the lower side of the substrate, which is also oxidized _o C external copper surfaces and "virgin" or uncontaminated inner copper surface is C, and the aluminum Ai lower mating surface as completely as possible free of impurities.

Figure 4 shows a detail of a different embodiment in which a single layer of copper foil C is applied to the aluminum backing layer A. FIG. This embodiment of the invention may be used depending on the design of the printed circuit board and the requirements of the printed circuit board. Except for containing only one layer of copper foil C, it is of the same construction as the embodiment shown in Figure 3. The copper foil layer C will serve as a functional element in the finished PCB and the aluminum carrier layer A will serve as a removable element.

Referring now to Figure 5, the laminated component 30 is illustrated as being the top layer of oxidized copper foils _oC outer copper surface faces up, and at one corner - peeled back - for easier understanding. The standard copper foil board size used to make printed circuit boards today is 305 x 305 mm (12 x 12), another preferred size is 460 x 612 mm (18 x 24), although 1224 x 920 mm (48 x 72). 1224x920 mm sheets are preferably cut into four 460x612 mm sheets. Of course, intermediate size copper foil sheets other than the sizes indicated are often used.

The component 30 shown in Figure 5 comprises a commercial grade aluminum backing layer A, preferably having a thickness in the range of 0.25 to 0.38 mm. On top of the substrate A is a copper foil sheet as in the example above

EN 216 987 Β is a semuncuncular copper foil having a thickness of approximately 18 µm. The folded corner reveals the inner or "virgin" surface of the component shown, i.e. the aluminum surface Aj and the inner copper surface Cj.

A resilient adhesive strip 40 is applied circumferentially along the edge of component 30 and connects the non-contaminated inner copper surface C and the aluminum surface A 1 along their edges. Because the contact surfaces are "virgin", or at least as clean as is physically possible, the adhesive strip 40 provides a substantially non-contaminated core CZ in the area inward of the edges of the superimposed sheets. This central CZ zone is not interconnected along the interface.

The elastic adhesive strip 40 is located in the adhesive zone 42 in Figure 5 and along the edge of component 30. This zone may be 2.5 to 25 mm wide, depending, in part, on the requirements for the final product and partly on the size of the aluminum sheet and copper sheet used to make the component 30. In our experiments, we have found that a strip of adhesive strip 40 having a width of approximately 1.5 to 2.4 mm performs well, although, as mentioned above, the width of this strip in the range of 0.25 to 12.5 mm can take any value from the size of the sheets to be laminated. depending on the thickness and may be approximately 25-127 µm, with a 25-50 µm thickness being particularly preferred.

The central zone CZ is delimited by a boundary 44 extending from the adhesive strip 40 to the interior of the sheets. While the finished printed circuit board will contain this central zone CZ, the strip 46 running around component 30 extends outwardly from the boundary 44, but further away from the dashed line 42. This outer peripheral strip 46 of component 30 is often used to detach small printed circuit board parts for quality control use. After the printed circuit board sandwich cores - often ten such sandwich cores - have been assembled and combined by heating and extrusion and then dried, the printed circuit boards are cut to size along the inner boundary of the adhesive zone, indicated by the dotted line 42 in the drawing.

In this way, the flexible adhesive strip 40 protects the copper and aluminum layers before and during manufacture from the penetration of dielectric layer dust or other contaminants from the air, material processing, fingers of the assembler, etc. can get there.

While the structure of the copper-aluminum-copper component 30 has been shown with a single copper foil C on the aluminum substrate A, the present invention can be applied in the same manner and with results as shown in Figs.

4. This means that the copper foil C can be attached to both sides of the aluminum substrate A. In the finished product, both copper foils C form a functional element of the individual printed circuit boards, while the aluminum A between them forms a disposable element - a separator board.

In the assembly of Figure 3, one surface of the copper foils C and the aluminum substrate A are both A; its surface is virtually 'virgin' with no dirt. These uncontaminated inner copper surfaces of copper foil C are bound to the opposite unpaired surface A of the aluminum substrate A by a flexible strip of adhesive 40 along the edges of the plates to form two substantially uncontaminated central CZ zones on either side of the aluminum substrate.

Although the invention has been described by way of example in the manufacture of printed circuit boards, the invention is also applicable to laminating processes in which some high purity base laminates have to be produced prior to the final product.

The essence and main principles of the invention can also be usefully applied in the production of credit cards requiring extreme purity. In this case, the substrate A may be made of aluminum, and in our examples the foil formed of copper sheets may be made of plastic. Of course, other suitable materials may be used as carriers.

As shown in Figure 5, the component 30 shown has four flexible, water-soluble adhesive islands 50 which connect one surface of the superimposed sheets to each other at predetermined locations. These adhesive islands 50 are located inwardly of the edges of the previously bonded sheets, i.e., inwardly of the elastic adhesive strip 40, outward of the boundary 44 separating the central zone CZ from the extreme test strip. In the illustrated embodiment, the adhesive islands 50 are formed about half of the side lengths at opposite ends of the component 30, and in the case shown may be rectangular, more precisely square, but of course other shapes. Their exact location depends on the location of the anchor pins at any given time.

The adhesive islands 50 have a cross-section of about 260 mm ² , which ensures that the medium-sized locating pins are unobstructed. Of course, depending on the size of the printed circuit board and the diameter of the locating pins, the cross-section of the adhesive islands 50 may be in a different range, such as 65 to 650 mm ² . The adhesive may be 13 to 130 µm thick, with a range of 25 to 50 µm being preferred.

The glue islands 50 may also be formed out of the center or centerline so that they can be connected by means of locating pins appropriate to the respective stamping technology. Individual plates of component 30 are punched or drilled at locations corresponding to the adhesive islands 50 so as to be able to accommodate positioning pins during preparation for extrusion.

As shown in Figure 6, component 30 may be pierced, pierced, or etched. The locating pin befo5

The hole 52 in the figure is oblong, but its shape is determined or at least influenced by the shape of the anchor pins used. Each of the elongated holes 52 is narrower (horizontal in the drawing) m slightly larger than the diameter of the locating pin (if a cylindrical locating pin is used) and larger in the drawing, vertical M, to permit insertion of the locating pins in the perfectly aligned position of component 30. The longitudinal axis M of the hole 52 is perpendicular to the edges of the plates 30 which form the component 30, while its minor axis M extends parallel to the edges of the plates.

Figure 2 shows two printed circuit boards made using the new component 30 laminated according to the invention. The sandwich core 10 having the same structure as the laminated sandwich core 10 described in Figure 1 is sandwiched between three components 30 of the present invention to form a sandwich structure. This assembly does not require the stainless steel sheets, release liners or coated aluminum mentioned in Figure 1. The resulting printed circuit board, on the other hand, will be identical to the structure shown in Figure 1.

The film layers 7 and 9 shown in Figure 2 form the upper and lower layers of the subsequent printed circuit boards located above and below the printed circuit board shown. These printed circuit boards are omitted from Figure 2. Often ten such six-layer printed circuit boards can be placed in a single pile or book, which can be simultaneously processed and dried. If the stacked books forming the book result in more, for example, ten printed circuit boards, the stamping pressure on the book forces the molten dielectric layer to wrap around the pins and flow along their surface. This flow passes through the ten stacked printed circuit board assemblies and slides along each layer along the copper surfaces. This causes not only contamination but also separation of layers and one of the main causes of waste. The purpose of the islands 50 to seal the clean connection C _(internal copper surfaces and the aluminum _(between surfaces of the heating and pressing during the prepreg penetration. As helyezőcsapokat host 52 holes are formed in the 50 area of the islands, the presence of adhesive prevents the molten dielectric layer from entering horizontally beyond the connection between the inner copper surfaces Cj and the aluminum A _s surfaces, thus eliminating the above problem.

Once such a printed circuit board has been laminated, dried and cooled, the individual printed circuit boards can be easily separated. The configuration shown in Figure 2 can be divided into two complete printed circuit boards as described above, by removing and disassembling the aluminum substrates of component 30. The top foil layer 7 forms the lowest functional layer of a third printed circuit board (not shown), while the bottom foil layer 9 forms the top functional layer of a previously unseen previous printed circuit board. The separation between the "virgin" or contaminated copper surface Cj and also the contaminated copper surface ₍ aluminum surface) is accomplished as shown in Figures 3 or 4.

Returning to Figure 2, the separation between each finished printed circuit board is performed along the pure copper surface Cj of the uppermost laminated component 30. In each case, the aluminum substrate A is separated from the copper foil C for each of the three components, and the lower copper foil C is bonded to its adjacent laminate sandwich core and the aluminum is removed, recycled, or used for other purposes.

Because of its fragility and vulnerability, this thin copper foil C was glued to its adjacent aluminum A substrate, making component 30 stiffer and easier to handle, resulting in significantly less scrap due to damage to the copper foil layers.

The use of adhesive media, regardless of their material, serves the purpose of the user or manufacturer in using thin layers of copper foil over printed circuit boards, and greatly contributes to the automation of the manufacturing process in that all thin layers in the present invention gets enough physical stiffening.

In fact, due to the presence of adhesive strips 40 which bind the copper and aluminum layers together, neither the dielectric powder powder nor other impurities can reach the CZ central zone for subsequent processing, either prior to production or during each manufacturing operation.

Because the locating pins are placed in or in place on the glue islands 50, due to the adhesive material that surrounds the locating pins, the molten dielectric layer cannot slip between the aluminum and copper layers, and cannot exert a deleterious separation and contamination effect. Subsequently, the water-soluble adhesive constituting the adhesive islands is simply washed out of any printed circuit board already made by any industrially-applied cleaning or washing process, the printed circuit boards are cut to size, but aluminum layers which are not part of the printed circuit boards are removed before cutting. .

In view of the above, it is readily apparent that the 30 components have been fully accomplished.

Claims (8)

Component for the production of a printed circuit board, which is a laminated multilayer sandwich consisting of dielectric layers and foil plate (s). It further comprises a laminate of copper foil (C) forming a functional element of the printed circuit board and an aluminum sheet of a removable element, wherein one surface of the copper foil (C) and the aluminum sheet is free of dirt and comprising an elastic adhesive strip (40) connecting the non-contaminated surface of the copper foil (C) sheet and the aluminum sheet along the edge of the sheet, thereby defining a substantially non-contaminated central zone (CZ); they come into direct contact with each other without binding or adhesive. Component for the manufacture of a printed circuit board comprising laminated multilayer sandwich cores composed of dielectric layers and foil plate (s), characterized in that, furthermore, two copper foil (C) plates and a removable element form a functional element of the finished printed circuit board. comprising a laminate having both copper foil (C) plates and an aluminum sheet having both surfaces contaminated and bonded to each other, and having the two copper foil (C) sheet and aluminum sheet non-contaminating surfaces along the edges of the sheets, (CZ) comprises a defining elastic adhesive strip (40). 3. A component for manufacturing a printed circuit board comprising laminated multi-layer sandwich cores consisting of dielectric layers and foil plate (s), further comprising a copper foil (C) plate and a removable element forming a functional element in the finished printed circuit board. comprising a laminate, wherein each surface of the copper foil (C) sheet and the aluminum sheet forms a non-contaminated and adherent surface and at least one adhesive seal (50) connecting the non-contaminated surfaces of the sheets to the flexible sheet. Component for the production of a printed circuit board comprising laminated multilayer sandwich cores consisting of dielectric layers and foil plate (s), characterized in that, furthermore, two copper foil (C) plates and a removable element form a functional element of the finished printed circuit board. comprising a laminate consisting of one surface of the two copper foil sheets (C) and both surfaces of the aluminum sheet which are non-contaminated and interconnected and at least one flexible water-soluble adhesive seal between the edges of the bonded sheets ( 50). Component for the manufacture of a printed circuit board comprising laminated multilayer sandwich cores composed of dielectric layers and foil plate (s), characterized in that the copper foil (C) plate forming a functional element of the finished printed circuit board and the aluminum plate forming a removable element comprising a laminate, wherein one surface of the copper foil (C) plate and the aluminum sheet forms a non-contaminated and interconnected surface, and a central zone (CZ) connecting the non-contaminated surface of the copper foil (C) plate and the aluminum sheet ) comprising a plurality of elastic adhesive strips (40) in which, in the region of the central zone (CZ), the sheets are in direct contact with one another without binding or adhesive and at least one elastic, water-soluble, It comprises an adhesive seal (50) formed on the edges of the assembled sheets connecting its free surfaces. Component for producing printed circuit boards, comprising laminated multi-layer sandwich cores consisting of dielectric layers and foil plate (s), characterized in that, furthermore, two copper foil (C) plates forming a functional element of the finished printed circuit board and forming an aluminum element comprising a laminate having two surfaces of copper foil (C) and an aluminum sheet having a non-contaminated and interconnected surface, and a central area joining the non-contaminating surface of the two copper foil (C) plates and the aluminum sheet along the edges thereof. (CZ) comprising an elastic adhesive strip (40) and further comprising at least one resilient, water-soluble adhesive formed between the edges of the assembled sheets and joining the non-contaminating surfaces of the sheets. contains an island (50). Component according to claim 1, 2, 5 or 6, characterized in that the elastic adhesive strip (40) has a width in the range of 0.25 to 12.7 mm and a thickness in the range of 25 to 50 µm. Component according to any one of claims 3, 4, 5 or 6, characterized in that the adhesive islands (50) have an area of 0.65-6.5 cm ² and a thickness of 12-127 µm.